Impregnation of a nonwoven fabric

ABSTRACT

A coating composition which imparts certain desired properties, such as opacity, water repellency, and fire resistance, to a nonwoven fabric comprising randomly arranged continuous filament polymeric fibers. The ingredients of the coating not only impart the desired properties but also are compatible with one another. The coating is applied on an apparatus wherein the tension and the temperature of the fabric are controlled to prevent elongation thereof.

United States Patent [72] Inventor Robert D. Feitlowitz Ridgewood, NJ.[21] Appl. No. 791,071 [22] Filed Jan. 14, 1969 [45] Patented Nov. 16,1971 [73] Assignee DHJ Industries Inc.

New York, N.Y.

[54] IMPREGNATION OF A NONWOVEN FABRIC 2 Claims, 1 Drawing Fig.

[52] US. Fl 117/7, 117/68,117/137,l17/l4OA [51] Int. B44d 1/46, C0913/28, B321: 27/12 [50] Field of Search 117/7, 137, 140 R, 135.5

[56] References Cited UNITED STATES PATENTS 1,955,888 4/1934 Nollau117/136 UX 2,191,362 2/1940 Widmer et a1. l 17/135.5 2,443,566 6/1948Love1and..... 117/ 137 UX 2,446,864 8/1948 Abrams ll7/135.5 UX

2,697,678 12/1954 Ness et al 117/7 X 2,983,627 5/1961 Williams.. 117/140X 3,009,832 11/1961 Burkitt 117/140 X 3,116,163 12/1963 Nottebohm et a1117/140 3,185,582 5/1965 Alegre 117/140 X 3,219,478 1l/l965 Wagner117/137 X 3,245,942 4/1966 Limperos l17/l35.5 X 3,341,394 9/1967 Kinney161/150X FOREIGN PATENTS 637,222 2/1962 Canada 117/137 727,163 3/1955Great Britain 117/137 Primary Examiner-William D. Martin AssistantExaminer-Harry J. Gwinnell Attorney-Kane, Dalsimer,,l(ane, Sullivan andKurucz ABSTRACT: A coating composition which imparts certain desiredproperties, such as opacity, water repellency, and fire resistance, to anonwoven fabric comprising randomly arranged continuous filamentpolymeric fibers. The ingredients of the coating not only impart thedesired properties but also are compatible with one another. The coatingis applied on an apparatus wherein the tension and the temperature ofthe fabric are controlled to prevent elongation thereof.

S65 7 60A f 1116 ENS/0N call/Awning g? IMPREGNATION OF A NONWOVEN FABRICBACKGROUND AND SUMMARY OF THE INVENTION This invention relates to acoating process for improving the properties of certain nonwovenfabrics, and to the solutions for use in such a process. Moreparticularly, the invention relates to a process for imparting certaindesired physical properties to a nonwoven fabric of the type comprisinga plurality of randomly arranged continuous polymeric fibers.

In recent years, nonwoven fabrics have generated a great deal ofinterest in the textile industry. Typically, these fabrics comprise acoherent sheet of entangled and/or bonded fibers without the fibersbeing first spun into yarns and interlaced by weaving, knitting, orother similar process. The anticipated large scale use of these fabricsfor apparel and other commercial uses has not been realized howeversince the nonwoven fabrics lack high tensile strength and resistance totear.

More recently, nonwoven fabrics having superior tensile and tearstrength have been developed which comprises continuous filamentpolymeric fibers distributed in the fabric web in a homogeneous randommanner. A fabric of this type is described in the U.S. Pat. to Kinney,No. 3,341,394 and is sold by E. I. duPont de Nemours and Company underthe trademark Reemay. While these continuous filament fabrics providesignificantly improved strength, they lack several properties which areessential to most commercial uses. In particular, these nonwovenmaterials lack sufficient opacity to permit use as a garment, they arenot sufficiently flameproof, and they lack water repellency.

Various coating solutions for these high-strength nonwoven fabrics havebeen proposed and tested in an effort to improve the physical propertiesof the material. However, the known coating solutions have proven to beunsatisfactory since the various ingredients necessary to impart thedesired characteristics have been found to be incompatible with eachother. It was not until the present invention that a coating solutionhas been found which both imparts the necessary properties to the fabricand which has compatible ingredients.

It is therefore an object of the present invention to provide a methodof treating a high-strength nonwoven fabric of the described type toproduce a product suitable for use in wearing apparel.

It is also an object of this invention to provide a specific formulationfor a coating solution to be applied to the nonwoven fabric and whichimparts certain desired physical properties to the material. Moreparticularly, it is an object of this invention to provide a specificformulation which imparts opacity, water repellency, fire resistance,and various combinations of these properties to a material of thedescribed type.

In addition, it is an object of this invention to provide a method forapplying specific coatings to a nonwoven substrate which is compatiblewith the coating solution and which does not injure the fabric substrateby excess heat or tension.

These and other objects and advantages of the present invention willreadily suggest themselves to one skilled in the art from the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 of the drawing is a schematic representation of the equipmentutilized in the coating operation of the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thecoating apparatus utilized with the present invention is indicatedgenerally at 10. The fabric 12 is initially fed from its roll 14 at oneend of the machine to the scray l6, and then to the coating station 18.There are several methods presently available for applying coatingsolutions to a textile substrate, and subject to the specific parametersmentioned below, any of these known methods can be adapted for use withthe present invention. In the present embodiment, the kiss" roll methodis illustrated. Here, the coating is applied from an applicator roll 21as the fabric is drawn between the roll 21 and a backup roll 22. In thismanner, the coating penetrates the fabric and is applied evenly on boththe top and bottom surfaces.

Once coated, the fabric is passed through a conventional tensioningdevice 24 to a dryer where the excess solvent and/or water isevaporated. A suitable dryer for this purpose typically comprises a gasfired predryer 26 positioned in series with a plurality of steam heatedcylinders or cans 28. In this instance, the fabric is initially heatedin the predryer to prevent an abrupt temperature change when the firstcan is reached. It will be noted that each side of the fabric receivesheat alternatively as the fabric travels from one drying can to thenext.

The steam pressure in the cylinders or cans 28 is preferably graduatedfrom a pressure of approximately 5 to 10 pounds per square inch and atemperature of approximately F. in the initial cans, to approximately 45pounds per square inch and 300 F. in the middle and subsequent cans. Bythis arrangement, a gradual increase in temperature is obtained alongthe first half of the cans and a constant elevated temperature ismaintained in the second half of the cans.

Since the substrate utilized in the present invention is of light weightand somewhat sheer, it is necessary to use care to deliver the fabricunder as little tension as possible in order to eliminate elongation ortearing which might otherwise occur. In practice, it has been found thatit is necessary to control the tension to a range below approximately 1pound per square inch during the coating and drying operations.Automatic feed controls are therefore incorporated in the machine topermit overfeeding or underfeeding different portions of the fabric sothat proper tensioning can be assured.

In addition to accurately controlling the fabric tensioning, it is alsoimportant that the applied heat be accurately controlled. In particular,exposure of the fabric to a temperature above approximately 310 F. Willresult in the loss of tensile strength and thus permit the material tostretch or elongate. In addition, a fabric of this type is sensitive toan abrupt temperature change which may similarly cause the material tolose tensile strength.

To accurately control fabric tension during the drying operation, one ormore tensioning devices are strategically positioned in the system. Thusin the illustrated apparatus, a tensioning device 30 is positionedmidway along the length of the heated drums. The device 30 includes aweighted tensioning roller 31 which is designed to be positioned betweenthe electric eyes 32 and 33 when the proper degree of tensioning ispresent. If the tension is too great, the roller 31 will rise until theeye 32 is actuated which in turn causes a compensating correction byvarying the speed of an appropriate number of the drums. If the tensionis too low, the eye 33 is actuated which in turn causes a reversecompensation by the variable speed drums.

Since the fabric lacks tensile strength when heated, it is passed acrossthe cooling cans 35 and 36 before being positioned on the takeup roll38. Also, an electric eye tensioning device 40 may be positioned betweenthe drying cans and the cooling cans to prevent undue tensioning duringthis critical period. The electric eye 40 functions in a manner similarto that of the eye 30 and acts to control the speed of the takeup roll38.

As indicated above, it is a primary object of the present invention toprovide a coating composition which imparts the desired properties ofopacity, water repellency, and flame resistance to a nonwoven fabric ofthe described type. The following examples illustrate preparations ofspecific coating compositions which have been found to impart theindicated properties and wherein the individual ingredients are compatible with one another.

for the coating composition is employed:

Ingredient Percent By Weight I. An inert filler 10 to 70 2. An emulsionconsisting of one part natural gum ether to approximately 1 1 partswater 8 to 15 3. An acrylic emulsion binder 15 to 40 4. Diammoniumphosphate 10 to 15 5. Water to 20 In the above composition, the inertfiller is provided to furnish the desired opacity to the fabric, and maycomprise a titanium dioxide pigment such as is sold by lnterchemicalCorporation, Hawthorne, NJ. under the trademark AQUA PRINT 5159. Thefiller may also consist of a suitable clay or calcium carbonate.

The natural gum ether is designed to act as a thickener for the mixture,and is defined in the book Textile Chemicals and Auxiliaries, by Speeland Schwarz, Reinhold, 1957, at page 270 as a cold water-soluble locustbean gum prepared by etherification. A suitable ether of this type ismanufactured by Polymer Industries, Inc., Springdale, Conn., under thetrademark POLYGUM 272. The emulsion is prepared by sifting the POLYGUM272 into water using one part POLYGUM 272 to l 1 parts water.

An acrylic emulsion binder of the type utilized in the above formulationis sold by Rohm and Haas Co., Philadelphia, Pa., under the trademarkRHOPLEX HA-8.

The diammonium phosphate acts as a catalyst to facilitate cure of thebinder. It is noted that while diammonium phosphate is norrna1ly,a fireretardant, it is not present in sufficient quantity in the presentformulation to provide this property in any measurable degree.

The indicated amount of water may be added to the above formulation togive desired consistency to facilitate application of the coating to thefabric.

FORMULATION NO. 2

To provide an opaque and water: repellent finish, the followingformulation is employed:

In the above formulation, the inert filler may comprise a titaniumdioxide pigment, clay, or calcium carbonate as further described underFormulation No. l.

A vinyl chloride emulsion binder suitable for use with the aboveformulation is sold by the National Starch & Chemical Corp., New York,N.Y. under the trademark BINDER 78-5159.

The melamine based resin dispersion is designed to add water repellencyto the fabric. A suitable composition is sold by American Cyanamid Co.,Bound Brook, NJ. under the trademark PERMEL B. which is identified bythe manufacturer as a water-repellent aqueous melamine aldehyde resindispersion used to provide a soft finish and increase the tear strengthof cotton, rayon, wool and synthetic fabrics.

FORMULATION NO 3 The following formulation is designed to provideopacity, fire resistance, and water repellency to a nonwoven fabric ofthe described type:

Ingredient Percent By Weight I. An inert filler 15 to 50 2. A phosphateplasticizer to 20 3. A vinyl chloride emulsion binder 8 to 20 4. Amelamine based resin dispersion 20 to 30 5. A flame retardant salt to 25In the above formulation, the inert filler, the vinyl chloride emulsionbinder, and the melamine based resin dispersion are all similar incomposition and function to the corresponding 5 ingredients inFormulation No. 2. Water may also be added to the formulation to providethe desired consistency.

The phosphate plasticizer may consist of a variety of phosphatematerials such as tricresyl phosphate, trioctyl phosphate or cresyldiphenyl phosphate. A suitable plasticizer of this type is sold by theStauffer Chemical Company, Los Angeles, Cal., under the trademark LINDOLwhich is tricresyl phosphate.

The flame retardant salt typically comprises an inorganic phosphorouscompound. A compound of this nature is sold under the trademarkFLAMEPROOF No. 736 by the Apex Chemical Company, Elizabethport, N].which is described by the manufacturer as an inorganic phosphate whichis soluble in water.

While the resins employed in the above formulation are capable of curingwith heat alone, a catalyst may be added to lower the temperature atwhich they will cure. Acid catalysts based on ammonium salts or freeacid catalysts such as oxalic or citric acid are commonly employed forthis purpose.

FORMULATION NO. 4

The following formulation may be utilized to provide an opaque and fireretardant finish to a nonwoven fabric of the described type:

Ingredient Percent by Weight I. An inert filler 15 to 50 2. Phosphateplasticizer 10 to 25 3. An emulsion ofa thermoplastic resin 2 to 25 4. Aflame retardant salt I to 20 5. An acrylic polymer 10 to 30 6. Water 5to 20 The inert filler, the phosphate plasticiser, and the flameretardant salt, are similar to the corresponding ingredients describedabove in Formulation No. 3.

The emulsion of a thermoplastic resin employed in the above formulationis copolymer of vinyl chloride and vinyl acetate and this emulsion issold by the Apex Chemical Company under the trademark APEX BINDER No. 3.

The acrylic polymer is provided to give added thickness or viscosity tothe formulation and this polymer is sold by Rohm & Haas Co. under thetrademark ACRYSOL ASE-60.

I claim:

1. A method of impregnating a nonwoven fabric consisting of randomlyarranged continuous filament polymeric fibers which are bonded togetherat crossover points to provide an opaque fire-resistant product,comprising:

applying to said fabric an aqueous composition containing a thickenedemulsion resin binder in which the resin is selected from the groupconsisting of a polymerized acrylic resin and copolymer of vinylchloride and vinyl acetate, and an inert opacifying finely dividedfiller selected from the group consisting of titanium dioxide, clay, andcalcium carbonate;

tensioning said impregnated fabric while applying said coating andfeeding the fabric to a heat-curing station at a uniform tension ofslightly less than about 1 pound per square inch, whereby the fabricdoes not undergo excessive elongation or tearing; and,

subjecting said impregnated fabric to a gradually increasing temperatureof from approximately 100 F. to a temperature below 310 F. for a timewhich is sufficient to set the coating and cure the fabric.

2. A method as claimed in claim 1, wherein said coating is applied froman applicator kiss roll on both the front and back surfaces of thefabric, said inert filler is used in an amount of 10-70 percent byweight of the coating composition and is titanium dioxide, said resinthickened emulsion is thickened with etherified locust bean gum ether inan amount of 8-15 percent, said emulsion binder is an emulsion of apolymerized acrylic resin, and said composition contains diammoniumphosphate in an amount of 10-15 percent. 5

2. A method as claimed in claim 1, wherein said coating is applied from an applicator ''''kiss'''' roll on both the front and back surfaces of the fabric, said inert filler is used in an amount of 10-70 percent by weight of the coating composition and is titanium dioxide, said resin thickened emulsion is thickened with etherified locust bean gum ether in an amount of 8-15 percent, said emulsion binder is an emulsion of a polymerized acrylic resin, and said composition contains diammonium phosphate in an amount of 10-15 percent. 